Release explosion damper

ABSTRACT

A clamping and/or spreading tool comprising a push or pull rod to which a mobile jaw is fixed, a fixed jaw, a gear mechanism which can be used to move the mobile jaw towards or away from the fixed jaw by moving the push or pull rod in a clamping or spreading direction, and to apply clamping and/or bracing forces between the jaws, and a lock used to block movement of the push or pull rod in an opening direction opposing the clamping or spreading direction, in order to maintain clamping and/or spreading forces produced between the jaws. A mechanism for dissipating the stored clamping and/or spreading forces enables an absorption movement of the push or pull rod in the opening direction along a pre-determined absorption course, and especially detachably blocks an absorption movement of the push or pull rod over the predetermined absorption course, in the opening direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority benefits under 35 U.S.C. §371 toInternational Patent Application No. PCT/EP2005/005193, filed Mar. 12,2005, International Patent Application No. PCT/EP2004/013979, filed Dec.8, 2004, and German Patent Application No. 10 2004 024 862.1, filed May19, 2004, all of which are incorporated herein by reference in theirentirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND

1. Technical Field

The invention relates to a clamping and/or spreading tool, comprising apush or pull rod to which a movable jaw is fixed, a stationary jaw, agear mechanism by which the movable jaw is movable towards or away fromthe stationary jaw by displacement of the push or pull rod in a clampingor spreading direction and by which clamping and/or spreading forces areapplicable between the jaws, further comprising a lock which blocksdisplacement of the push or pull rod in opening direction opposite tothe clamping or spreading direction so as to maintain the clampingand/or spreading forces generated between the jaws.

2. Background Art

DE 103 35 365 A1 discloses a clamping or spreading tool of this kindwhich can generate very great clamping forces between the stationary andmovable jaws. To accomplish that, the pivot arm is pivotably mounted ata clamping side of the push or pull rod on a support which holds thestationary jaw. The point of contact at which the actuating arm canintroduce actuating forces into an entraining slide element of the gearmechanism likewise is provided at the clamping side of the push or pullrod between the swivel joint and the push or pull rod. The leverage thusachieved is apt to provide clamping or spreading forces of up to 3000Newton between the clamping jaws when the clamping tool is manipulatedby one hand.

Once great tensioning forces have been generated, it may happen thatactuation for release of the draw-back lock retaining the high tensionwill cause the movable jaw to be propelled explosively away from thestationary jaw. Analyses have clearly demonstrated that the clampingtool, especially the material of the clamping jaws, when tensioned,behaves like an elastic system deforming elastically in accordance withthe tension created. Discharging of the clamping tool unloads the storedtension in correspondence with the modulus of elasticity inherent in thesystem by a shock-like movement of the push or pull rod in openingdirection. The stored potential tensional energy is converted intokinetic energy of the push or pull rod. And it may happen that the pushor pull rod is launched right through the support of the stationary jaw.

Since it is preferred to keep a low friction profile of the push rodwithin the support to permit easy displacement and adjustment of thepush or pull rod, the release of very great tensional forces may let thepush or pull rod, together with the movable jaw, glide through thesupport without any deceleration, whereby not only the workpiece to betreated may be damaged but also the person handling the tool may behurt.

SUMMARY

It is an object of the invention to provide a clamping or spreading toolwhich permits the energy stored in the tensioned clamping or spreadingtool to be discharged, especially non-explosively, at the same timewarranting simple manipulation not susceptible of causing injury.

This object is met by the features of claim 1.

Thus a clamping and/or spreading tool comprises a push or pull rod towhich a movable jaw is fixed, a stationary jaw, a gear mechanism bywhich the movable jaw is movable towards or away from the stationary jawby displacement of the push or pull rod in a clamping or spreadingdirection and by which clamping and/or spreading forces are applicablebetween the jaws, and further comprises a lock which blocks displacementof the push or pull rod in opening direction opposite to the clamping orspreading direction so as to uphold the clamping and/or spreading forcesgenerated between the jaws. In accordance with the invention, aconventional draw-back lock as described in DE 39 17 473 A1 or anentraining slide element canted with respect to the push or pull rod bycoercive means, such as a compression spring, and embodied by a wedgingplate which is capable of blocking the displacement of the push or pullrod due to its canting, may be regarded as the lock.

According to the invention the clamping and/or spreading tool comprisesa mechanism for dissipating the clamping and/or spreading forces stored,said mechanism allowing especially controlled absorption displacement ofthe push or pull rod in opening direction along a predetermined, limitedabsorption path. The limitation of the absorption path is obtained by ablocking effect of the mechanism which does not come to bear until theabsorption displacement of the push or pull rod in opening directiongoes beyond the predetermined absorption path. And it blocks the furtherabsorption displacement of the push or pull rod in opening directionwith respect to the stationary jaw. The limitation of the absorptiondisplacement may be removable to guarantee unblocked displacement of thepush or pull rod for quick adjustment of the jaws.

The invention makes it possible to assure that the stored tensioningand/or spreading forces, when set free, will not let the push or pullrod become displaced in space like a projectile. Instead, loosening ofthe clamping and/or spreading tool will move the jaws only a little inopening direction, especially just a few millimetres, preferably withoutlosing contact with the workpiece. During this absorption displacementat least part of the clamping and/or spreading forces, preferably all ofthese forces, will be dissipated by friction or damping. What remains ofthe clamping and/or spreading forces is retained by the blocking effectof the mechanism initiated after the absorption displacement. In thismanner the dissipation of the stored clamping and/or spreading forcescan be controlled, and the absorption displacement of the push or pullrod upon release of the tension is restricted to a desired extent.

In a further development of the invention the mechanism is adapted to beactivated, especially by being actuated by the operator thereof, so thatthe absorption displacement of the push or pull rod in opening directionalong the absorption path is allowed and carried out independently uponactivation. After the absorption displacement a limitation of theabsorption displacement takes hold automatically.

The mechanism, preferably, can be activated only upon release of theblocking effect of a lock, especially a draw-back lock.

According to a further development, the mechanism should be capable ofbeing activated only by release of the tensioned clamping and/orspreading tool, especially of the lock which is charged by clampingand/or spreading forces. It is preferred that the mechanism be or remaininactive when the clamping and/or spreading tool is not tensioned,especially the lock is not charged.

With a preferred further development of the invention, the lock can beshifted essentially in opening direction with respect to the stationaryjaw while the blocking effect is maintained to accomplish the absorptiondisplacement. The blocking effect of the lock is to be understood asmeaning that the displacement motion of the push or pull rod in openingdirection with respect to the lock itself is blocked. When shifting thelock per se, the push or pull rod is allowed to move in openingdirection, and this movement presents the predefined absorptiondisplacement. The lock is arranged in a support in such a way that itcan be shifted in opening direction while its blocking effect is upheldduring shifting, the support carrying the stationary jaw and holding thepush or pull rod for displacement.

A known clamping and/or spreading tool such as described in the abovementioned DE 103 35 365 A1 might be developed further by a mechanismaccording to the invention in that the spring biased release lever ofthe draw-back lock is supported so that it can be shifted, especially inopening direction, with respect to the support carrying the stationaryjaw, for example, by an eccentric rotary member to be actuated by theoperator. Shifting of the release lever, together with the push or pullrod which is canted with respect to the same, shortens the springexcursion of the elastically biased system at least in part, cancellingit entirely, if desired. The spring excursion is defined by elasticallydeformable clamping jaw parts of the clamping and/or spreading tool. Andthe elastic tensioning forces are dissipated.

Preferably, the lock can be shifted from a resting position in which itis set, especially forcibly upon actuation of the mechanism, into anabsorption end position at which its blocking effect sets in. Duringshifting, the blocking effect of the lock prevents displacement of thepush or pull rod with respect to the lock. Yet the push or pull rod,including the lock, is able to move in opening direction with respect tothe stationary jaw. The shifting distance of the lock may be limited,especially by an abutment formed on the support.

The shifting distance travelled by the lock during absorptiondisplacement, preferably, is equal or at least proportional to thepredetermined absorption path.

In a preferred further development of the invention the mechanismincludes a drive for shifting the lock in opening direction, togetherwith the push or pull rod which is locked to the same. A drive may beprovided for implementation by the operator, comprising an eccentricbearing for the lock. To implement an automatic drive, at least part ofthe clamping and/or spreading forces stored may be introduced into thelock to be shifted.

The blocking effect of the lock may be realized by forced canting of aplate-type lock with respect to the push or pull rod to blockdisplacement of the push or pull rod in opening direction.

The mechanism, preferably, comprises two plate-type locks for blockingthe displacement of the push or pull rod in opening direction. One ofthem may be shifted or moved with respect to the stationary jaw,essentially in opening direction, especially parallel to the push orpull rod, to provide the absorption displacement, while maintaining itsforced canting. The other one is arranged stationarily with respect tothe stationary jaw, while maintaining its forced canting.

In further development of the invention, the forced canting of thestationary plate-type lock may be lifted before lifting the forcedcanting of the shiftable plate-type lock, especially offset in timeand/or distance.

When the forced canting of the stationary plate-type spring is liftedthe clamping and/or spreading forces set free preferably can beintroduced into the plate-type lock adapted to carry out shifting ortranslatory motion. They cause the shifting or displacing of theshiftable plate-type lock from a starting position into an end positionat which further shifting is prevented.

In a particular embodiment of the invention, the shiftable plate-typelock comprises a wedging plate which is forcibly canted to the push orpull rod so that displacement of the push or pull rod with respect tothe wedging plate in opening direction is blocked. The wedging platecontacts a movable place for engagement.

The wedging plate may be an entraining slide element of the gearmechanism embodied by a stepping gear. And the movable place forengagement is a location on the movable actuating arm of the steppinggear for transmitting the actuating force into the entraining slideelement.

The actuating arm may adopt a mid position at which the actuating arm ispositioned when unloaded by an operator, a stroke end position intowhich the actuating arm can be moved when actuated by an operator fordisplacing the push or pull roll in clamping or spreading direction, andan absorption end position, opposite to the stroke end position, intowhich the actuating arm can be moved for shifting the entraining slideelement, while maintaining the forced canting thereof. In the latterposition the actuating arm strikes against an abutment to present alimitation to the absorption displacement.

In a further development of the invention, the mechanism comprises adamper which dampens the absorption displacement of the push or pull rodalong the absorption path. The damper, preferably, is activated onlywhen the mechanism for absorption displacement of the push or pull rodin opening direction is activated. The damper may be formed by acentering spring, especially a compression spring which is adapted to betensioned by shifting of the lock in opening direction. The centeringspring may be disposed between a support holding the stationary jaw andthe actuating arm. Alternatively, the damper may be formed by a catchmeans by which the clamping or spreading forces set free are damped byfriction when the catch snaps into and out of engagement.

Preferably, the centering spring and a gear spring for canting theentraining slide element are tuned to each other in such a way that theactuating arm is forcibly located in mid position. From this position,lifting motion for the gear mechanism contrary to the gear spring andabsorption motion for the mechanism contrary to the centering spring areallowed.

The centering spring which is tensioned in the absorption end positionof the actuating arm can be relieved of tension by cancellation of theforced canting of the entraining slide element. It is especially therelaxing centering spring which urges the actuating arm into midposition.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, features, and characteristics of the invention willbe described in the description below of a preferred embodiment, withreference to the accompanying drawings, in which:

FIG. 1 is a side elevational view of an untensioned clamping and/orspreading tool according to the invention, showing a casing broken awayfor better viewing and free sections for better recognition of theinterior of the stepping gear and the mechanism according to theinvention;

FIG. 2 is a side elevational view of the clamping and/or spreading toolaccording to FIG. 1, in tensioned state, with a release lever alreadyhaving been partly actuated but not yet cancelling clamping forces;

FIG. 3 is a side elevational view of the clamping and/or spreading toolaccording to FIGS. 1 and 2, showing the mechanism according to theinvention in an intermediate phase in which the clamping forces arecancelled only partly;

FIG. 4 is a side elevational view of the clamping and/or spreading toolaccording to FIGS. 1 to 3, showing the mechanism according to theinvention in a final phase in which the clamping forces are cancelledcompletely;

FIG. 5 is a side elevational view of the clamping and/or spreading toolaccording to FIGS. 1 to 4, showing the release lever of the mechanismaccording to the invention in non-actuated state.

DETAILED DESCRIPTION

The clamping tool 1 shown in FIGS. 1 to 5 comprises a support 3 on whicha stationary jaw 5 is mounted and in which a push rod 7 is supported fordisplacement in longitudinal direction. Near the ends of the support 3,slide bearing portions 9 and 11 offering low sliding friction areprovided to support the push rod 7.

A movable jaw 13 is removably mounted at one end of the push rod 7. Itis oriented with respect to the stationary jaw 5 so as to create aclamping tool configuration, as may be seen in FIGS. 1 to 4. If themovable jaw 13 were to be mounted at the other end of the push rod 7 theconfiguration would be that of a spreading tool, not shown in thedrawings.

A handle member 17 is formed integrally with the support 3 at anactuating side 15 of the push rod 7. An actuating arm 19 is pivoted tothe support 3 in such manner as to allow swinging of the actuating arm19 in the direction of the handle member 17. The actuating arm 19 issupported on the support 3 by means of a swivel joint 21 disposed at aclamping side 23 of the push or pull rod 7. Below the swivel joint 21,the actuating arm 19 has a cylindrical projecting stop 25 in engagementwith entrainment plates of an entraining slide element 27.

The entraining slide element 27 is part of a stepping gear to beactuated by means of the actuating arm 19 for displacing the push rod 7in spreading and/or clamping direction S. The stepping gear comprises ahelical compression spring 29 disposed at the clamping side, orientedparallel to the push rod 7, and fitted under bias in a blind bore 31formed in the support 3. The helical compression spring 29 acts on theentraining slide element 27 below the cylindrical projecting stop 25.The helical compression spring 29 in mounted under such bias as to swingthe entraining slide element 27 in counterclockwise sense around thecylindrical projecting stop 25. Thereby the entraining slide element 27enters into forced canting engagement with the push rod 7. Canting ofthe entraining slide member 27 results in blocking movement of the pushrod 7 with respect to the entraining slide element 27 in openingdirection O, opposite to the clamping and/or spreading direction S. Theentraining slide element 27 thus acts in blocking sense on thedisplacement in opening direction O. Consequently the clamping forcesgenerated between the clamping jaws 5 and 13 can be maintained when theprojecting stop 25 has been moved in opening direction, stationary withrespect to the support 3.

The stepping gear, moreover, comprises a draw-back lock 35 formed by awedging plate 37 which is brought into canted blocking engagement withthe push rod 7, like the entraining slide member 27, around a stationarypoint for engagement 41 of the support 3. A compression spring 39disposed at the clamping side and a secondary spring 43 disposed at theactuating side cooperate to accomplish that. Arranging the compressionspring 39 and the secondary spring 43 as a pair has the additionaleffect of preventing that the wedging plate 37, too, is shifted inclamping direction S due to friction when the push rod 7 is displaced inclamping direction S.

The draw-back lock 35 further comprises a release lever 45 to beactuated by an operator, especially with a forefinger, so as to enterinto engagement with the lower end (covered up by component 61) of thewedging plate 37 to lift the canting thereof. The release lever 45 is inconstant contact with a tappet 49 which is spring-(47)-biased andsupported parallel to the push rod 7 in a longitudinal guideway 45formed in the support 3. A return spring 47 is disposed between aprojection 53 formed essentially in the middle of the tappet 49 and anabutment surface 50 of the support 3. Under bias, this spring serves topress the tappet 49 in the direction of the release lever 45.

A centering spring 61 is arranged between a spring stop 57 of thesupport 3 and an edge portion 59 of the actuating arm 19, attempting tourge the actuating arm 19 in the direction of the handle member 17. Atthe level of the support 3, the actuating arm 19 is shown in the drawingin dash-dot lines only for better recognition of the mechanism accordingto the invention.

When the actuating arm 19 is actuated, i.e. when the actuating arm 19 ispulled towards the handle member 17 the push rod is displaced inclamping direction S by virtue of the engagement of the projecting stop25 with the entraining slide element 27. Hereby the workpiece 63arranged between the clamping jaws 5 and 13 is gripped tight andclamping forces are imparted to the workpiece 63. A highly loaded,clamped workpiece 63 is to be seen in FIG. 2.

The description below relates only to the mechanism according to theinvention for dissipating the stored clamping and/or spreading forces atthe workpiece 63.

The basic concept of the mechanism according to the invention fordissipating the stored clamping and/or spreading forces resides inpermitting a certain predetermined absorption displacement of the pushrod 7 in opening direction O along a predetermined absorption path, withfurther displacement beyond the absorption path being blocked.

According to the invention, the absorption displacement may be obtainedby shifting the lock which blocks the displacement of the push rod 7 inopening direction. In the embodiment illustrated in FIGS. 1 to 5, thelock is formed by the forcibly canted entraining slide element 27. Thelock can be shifted because the entraining slide element 27 is movablein opening direction O, together with the push rod 7 canted to it, dueto the pivotable projecting stop 27 of the actuating arm 19 which stopis capable of carrying out translatory motion in longitudinal directionof the push rod 7.

Movability of the actuating arm 19 is granted by a free space 67 whichallows clockwise swinging of the actuating arm 19 from the mid positionillustrated in FIGS. 1 and 2 into an absorption end position (FIG. 3) atwhich the actuating arm 19 strikes against an abutment 69 formed on thesupport 3.

To make sure the actuating arm 19 does not get into the absorption endposition (FIG. 3) during normal operation, in other words before tensionstored between the clamping jaws 5 and 13 is relaxed, the centeringspring 61 is tuned in consideration of the leverage to the swivel joint21 and the leverage of the helical compression spring 29 to theprojecting stop 25. When at mid position, the actuating arm 19 isoffered a great lifting swing distance towards the handle member 17 and,by comparison, a relatively small absorption swing distance x (FIG. 2)towards the absorption end position.

It should be noted that the absorption swing distance x, i.e. the travelfrom mid position of the actuating arm 19 to the absorption end positionthereof corresponds substantially to the absorption travel of the pushrod 7 during which damping and dissipation are achieved of thetensioning forces set free.

The individual working steps of the mechanism for obtaining the desiredcontrolled absorption displacement and the limitation of the absorptiondisplacement of the push rod 7 will be described below.

FIG. 2 illustrates the clamping tool 1 in fully tensioned state whichmeans that the workpiece 63 is under clamping load between the clampingjaws 5 and 13. The clamping jaws 5, 13 and the clamped workpiece 63constitute an elastic system whose modulus of elasticity is determinedby the materials used. The exaggerated dumbbell deformation of theworkpiece 63 shown in the fig. is intended to demonstrate the elasticityof the system.

The clamping forces acting between the clamping jaws 5 and 13 weregenerated by the stepping gear upon actuation of the actuating arm 19.When the operator (not shown) lets go the actuating arm 19 the helicalcompression spring 29 moves the actuating arm 19 into mid position,shown in FIGS. 2 and 1. The centering spring 61 keeps the actuating arm19 away from the abutment 69.

When the clamping tool 1 is in the tensioned state shown in FIG. 2 theclamping forces are held only by the draw-back lock 35. The blockingeffect of the entraining slide element 27 is inactive since the cantedentraining slide element 27 cannot yet take up any forces because of theshiftability of the projecting stop 25 in opening direction O.

To release the clamping forces stored, in other words to discharge theworkpiece 63 of the tensioning load, the operator actuates the releaselever 45. In a first step of release, indicated in FIG. 3, the releaselever 45 is pulled further back, beyond the intermediate position shownin FIG. 2, until the wedging plate 37 is relieved of its canting to thepush rod 7. To this end, the release lever 45 presses against the lowerend (not visible) of the wedging plate 37, changing the position thereofin counterclockwise sense into a substantially vertical one. Hereby theblocking effect of the draw-back lock 35 is cancelled. Due to therelease of the draw-back lock 35 the elastic system composed of deformedclamping jaws and workpiece relaxes, as expected, displacing the pushrod 7 with respect to the support 3 in opening direction O. At the sametime, the entraining slide element 27 canted to the push rod 7 isshifted in correspondence with the absorption swing distance x inopposition to the centering spring 61 until the actuating arm 19 strikesagainst the abutment 69.

It is obvious that at the intermediate step of release, shown in FIG. 3,the wedging plate 37 is no longer canted and the actuating arm 19 is inits absorption end position. At this time, the centering spring 61 iscompressed. Part of the clamping forces has been dissipated, asindicated by the less strongly deformed workpiece 63.

The blocking effect of the entraining slide element 27 cannot take holdimmediately upon release of the draw-back lock 35 because, when in midposition, the actuating arm 19 is not fixed in clockwise sense. Insteadan absorption path x exists by virtue of the free space 67. It is onlywhen the actuating arm 19 is stopped by the abutment 69 and theprojecting stop 25 is fixed in opening direction O that blocking becomeseffective. This delayed entering into effect of the blocking by thecanted entraining slide element 27 stops the absorption movement of thepush rod 7 in opening direction.

Moreover, by overcoming the centering spring 61, the absorptiondisplacement of the actuating arm 19 and of the push rod 7 is damped. Inthis manner the clamping forces released which cause the push rod 7 tobecome displaced in opening direction O are partly dissipated, on theone hand, by frictional losses of the movement of the actuating arm 19and the push rod 7 in opening direction O and, on the other hand, by thebuild-up of tension of the centering spring 61. The remaining clampingforces are upheld by canting of the entraining slide element 27.

It is only when the release lever 45 is pressed further, as shown inFIG. 4 that the entraining projection 53 takes along the entrainingslide element 27 allowing it to swing in clockwise sense around theprojecting stop 25. Hereby the canted engagement between the entrainingslide element 27 and the push rod 7 is lifted and thus the locking orblocking effect of the entraining slide element 27 is cancelled. FIG. 4shows this final release step with the release lever 45 pulled all theway.

When both locks, the draw-back lock 35 and the blocking entraining slideelement 27 of the gear mechanism, have become fully loosened the desiredpossibility of free shifting of the push rod 7 at fully actuated releaselever 45 can be warranted. In this condition the operator can let thepush rod 7 slide through the support 3 under the influence of itsweight.

When the release lever 45 is let go the return spring 47 presses therelease lever 45 via the tappet 49 back into the starting position ofthe stepping gear and the mechanism, shown in FIG. 5. At the same time,the engagement of the entraining projection 53 lifting the canting ofthe entraining slide element is cancelled, and subsequently the blockingeffect of the draw-back lock 35 caused by canting is reestablished byfreeing the lower end of the wedging plates 37.

When the blocking effect of the entraining slide element 27 is given upthe actuating arm 19 is moved back into the mid position illustrated inFIG. 5 since there is no resistance and the centering spring 61 isstronger with the actuating arm 19 in this position.

The features disclosed in the specification above, in the figures anddrawings may be significant for implementing the invention in itsvarious embodiments, both individually and in any combination.

1. A clamping or spreading tool, comprising: a push or pull rod to whicha movable jaw is fixed; a stationary jaw; a gear mechanism by which themovable jaw is movable towards or away from the stationary jaw bydisplacement of the push or pull rod in a clamping or spreadingdirection and by which clamping or spreading forces are applied betweenthe jaws; a lock that blocks displacement of the push or pull rod in anopening direction opposite to the clamping or spreading direction so asto maintain the clamping or spreading forces generated between the jaws;and a force dissipating mechanism for dissipating the clamping orspreading forces stored that allows absorption displacement of the pushor pull rod in the opening direction along a predetermined absorptionpath and blocks absorption displacement of the push or pull rod in theopening direction beyond the predetermined absorption path upon releaseof the lock, said force dissipating mechanism including a release leverto release the lock and an entraining slide element to block theabsorption displacement of the push or pull rod in the opening directionbeyond the predetermined absorption path upon release of the lockwherein said release lever has a contacting member which is offset andcontacts a entrailing projection thereby producing said absorptiondisplacement.
 2. The clamping or spreading tool as claimed in claim 1,wherein the force dissipating mechanism is adapted to be activated by anoperator such that, upon activation, the absorption displacement of thepush or pull rod in the opening direction along the absorption path isallowed independently and, after the absorption displacement, anabsorption displacement limitation takes hold automatically.
 3. Theclamping or spreading tool as claimed in claim 1, wherein the forcedissipating mechanism can be activated only upon release of the blockingeffect of the lock.
 4. The clamping or spreading tool as claimed inclaim 1, wherein the force dissipating mechanism can be activated whenclamping or spreading forces are held at the lock.
 5. The clamping orspreading tool as claimed in claim 1, wherein the force dissipatingmechanism is or remains deactivated when the tool is not tensioned. 6.The clamping or spreading tool as claimed in claim 1, wherein the lockis shiftable essentially in the opening direction with respect to thestationary jaw, while maintaining its blocking effect, so as to providethe absorption displacement.
 7. The clamping or spreading tool asclaimed in claim 1, wherein the lock is arranged in a support in such away as to be shiftable in the opening direction while its blockingeffect is upheld, the support carrying the stationary jaw and holdingthe push or pull rod for displacement.
 8. The clamping or spreading toolas claimed in claim 6, wherein the lock is shiftable from a restingposition in which it may be forcibly adjusted upon activation of theforce dissipating mechanism into an absorption end position.
 9. Theclamping or spreading tool as claimed in claim 6, wherein shiftabilityof the lock is limited by an abutment formed on the support.
 10. Theclamping or spreading tool as claimed in claim 6, wherein the shiftdistance travelled by the lock during absorption displacementsubstantially equals the predetermined absorption path.
 11. The clampingor spreading tool as claimed in claim 1, wherein the force dissipatingmechanism comprises a drive for shifting the lock, with the push or pullrod-locked to the lock in the opening direction.
 12. The clamping orspreading tool as claimed in claim 11, wherein a the drive is to beimplemented by an operator and comprises an eccentric bearing for thelock, such that at least part of the clamping or spreading forces can beintroduced into the lock to be shifted.
 13. The clamping or spreadingtool as claimed in claim 1, wherein the lock is formed by a plate-typelock which is forcibly canted with respect to the push or pull rod toblock displacement of the push or pull rod in the opening direction. 14.The clamping or spreading tool as claimed in claim 1, wherein the forcedissipating mechanism comprises two plate-type locks, one of which isshiftable with respect to the stationary jaw essentially in the openingdirection for providing the absorption displacement while the forcedcanting with respect to the push or pull rod is upheld, whereas theother one is arranged stationarily with respect to the stationary jaw,maintaining the forced canting with respect to the push or pull rod. 15.The clamping or spreading tool as claimed in claim 14, herein the forcedcanting of the stationary plate-type lock can be lifted before theforced canting of the shiftable plate-type lock.
 16. The clamping orspreading tool as claimed in claim 14, wherein the clamping or spreadingforces released upon lifting of the forced canting of the stationaryplate-type lock can be introduced into the shiftable plate-type locksuch that the shiftable plate-type lock, together with the push or pullrod canted with respect to the same, are shifted from a startingposition into and end position at which further shifting is prevented.17. The clamping or spreading tool as claimed in claim 14, wherein theshiftable plate-type lock comprises a wedging plate which is forciblycanted to the push or pull rod so that displacement of the push or pullrod in the opening direction with respect to the wedging plate isblocked, said wedging plate contacting a movable place for engagement.18. The clamping or spreading tool as claimed in claim 17, wherein thewedging plate constitutes an entraining slide element of the gearmechanism designed as a stepping gear, and the movable place forengagement is presented by the location of power transmission from theentraining slide element into a movable, swingable actuating arm of thestepping gear.
 19. The clamping or spreading tool as claimed in claim18, wherein the actuating arm has a mid position at which the actuatingarm is positioned when unloaded, a stroke end position into which theactuating arm can be moved when actuated by an operator to displace thepush or pull rod in the clamping or spreading direction, and anabsorption end position, opposed to the stroke end position, into whichthe actuating arm can be moved for shifting the entraining slideelement, while maintaining the forced canting thereof, and at which theactuating arm strikes against an abutment present on a support forproviding limitation of the absorption displacement.
 20. The clamping orspreading tool as claimed in claim 1, wherein the force dissipatingmechanism comprises a damper which dampens the absorption displacementof the push or pull rod along the absorption path.
 21. The clamping orspreading tool as claimed in claim 20, wherein the damper is activatedonly when the force dissipating mechanism for absorption displacement ofthe push or pull rod is the opening direction is activated.
 22. Theclamping or spreading tool as claimed in claim 20, further comprising anactuating arm that operatively engages the entraining slide element, andwherein the damper is formed by a centering spring comprising acompression spring adapted to be tensioned by shifting of the lockessentially in the opening direction.
 23. The clamping or spreading toolas claimed in claim 22, wherein the centering spring is disposed betweena support which holds the stationary jaw and the actuating arm.
 24. Theclamping or spreading tool as claimed in claim 22, wherein the centeringspring and a gear spring for canting the entraining slide element areharmonized such that the actuating arm is forcibly positioned in a midposition out of which lifting motion for the gear mechanism contrary tothe gear spring and absorption motion for the force dissipatingmechanism contrary to the centering spring are allowed.
 25. The clampingor spreading tool as claimed in claim 22, wherein the centering springtensioned in the absorption end position of the actuating arm can berelieved of tension by lifting the forced canting of the entrainingslide element, the relaxing centering spring, at the same time, urgingthe actuating arm into the mid position.
 26. A clamping or spreadingtool, comprising: a push or pull rod to which a movable jaw is fixed; astationary jaw; a gear mechanism by which the movable jaw is movabletowards or away from the stationary jaw by displacement of the push orpull rod in a clamping or spreading direction and by which clamping orspreading forces are applied between the jaws; a lock that blocksdisplacement of the push or pull rod in an opening direction opposite tothe clamping or spreading direction so as to maintain the clamping orspreading forces generated between the jaws; and a force dissipatingmechanism for dissipating the clamping or spreading forces stored thatallows absorption displacement of the push or pull rod in the openingdirection and blocks absorption displacement of the push or pull rod inthe opening direction beyond a predetermined distance upon release ofthe lock, wherein the force dissipating mechanism comprises twoplate-type locks, one of which is shiftable with respect to thestationary jaw essentially in the opening direction for providing theabsorption displacement while the forced canting with respect to thepush or pull rod is upheld, whereas the other one is arrangedstationarily with respect to the stationary jaw, maintaining the forcedcanting with respect to the push or pull rod wherein said release leverhas a contacting member which is offset and contacts a entrailingprojection thereby producing said absorption displacement.
 27. Aclamping or spreading tool, comprising: a push or pull rod to which amovable jaw is fixed; a stationary jaw; a gear mechanism by which themovable jaw is movable towards or away from the stationary jaw bydisplacement of the push or pull rod in a clamping or spreadingdirection and by which clamping or spreading forces are applied betweenthe jaws; a lock that blocks displacement of the push or pull rod in anopening direction opposite to the clamping or spreading direction so asto maintain the clamping or spreading forces generated between the jaws;and means for dissipating the clamping or spreading forces stored thatallows absorption displacement of the push or pull rod in the openingdirection along a predetermined absorption path and blocks absorptiondisplacement of the push or pull rod in the opening direction beyond thepredetermined absorption path upon release of the lock.
 28. A clampingor spreading tool, comprising: a push or pull rod to which a movable jawis fixed; a stationary jaw; a gear mechanism by which the movable jaw ismovable towards or away from the stationary jaw by displacement of thepush or pull rod in a clamping or spreading direction and by whichclamping or spreading forces are applied between the jaws; a lock thatblocks displacement of the push or pull rod in an opening directionopposite to the clamping or spreading direction so as to maintain theclamping or spreading forces generated between the jaws; and a forcedissipating mechanism for dissipating the clamping or spreading forcesstored that allows absorption displacement of the push or pull rod inthe opening direction along a predetermined absorption path and blocksabsorption displacement of the push or pull rod in the opening directionbeyond the predetermined absorption path upon release of the lock, saidforce dissipating mechanism including: a release lever to release thelock; an entraining slide element to block the absorption displacementof the push or pull rod in the opening direction beyond thepredetermined absorption path upon release of the lock; and an actuatingarm operatively engaging the entraining slide element, the actuating armincluding a pivotable projecting stop for carrying out translatorymotion in the longitudinal direction of the push rod to allow shiftingof the entraining slide element.
 29. The clamping or spreading tool asclaimed in claim 28, wherein the actuating arm has a mid position atwhich the actuating arm is positioned when unloaded, a stroke endposition into which the actuating arm can be moved when actuated by anoperator to displace the push or pull rod in the clamping or spreadingdirection, and an absorption end position, opposed to the stroke endposition, into which the actuating arm can be moved for shifting theentraining slide element, while maintaining the forced canting thereof,and at which the actuating arm strikes against an abutment present on asupport for providing limitation of the absorption displacement.